Two lysosomal enzymes have been selected for intensive study: alpha-L- iduronidase, the enzyme deficient in the Hurler syndrome, and sulfoiduronate sulfatase, the enzymes deficient in the Hunter syndrome. The project focuses on improved methods of purification and assay in order to 1) improve diagnostic techniques; 2) study the properties of the enzymes; and 3) prepare enough purified enzyme for a clinical trial of enzyme replacement therapy.